1. Field of the Invention
The present invention relates generally to tire inspection equipment. More particularly, the invention concerns an apparatus for inspecting used truck tires prior to retreading.
2. Discussion of the Prior Art
A number of different types of equipment and processes have been suggested in the past for inspection of both new and used tires. Of particular interest has been the development of apparatus for use in the inspection of used tires to find hidden irregularities or defects prior to retreading the used tire casing. If a used tire casing, which has undetected defects is retreaded, pressurized air in the tire can leak through the defect and undesirably form a pocket between the outer surface of the casing and the new tread. Such a pocket can produce potentially dangerous steering, vibration and misalignment problems. Additionally, a buildup in pressure between the casing and the new tread can cause separation of the tread and create a potentially catastrophic condition.
Obviously, if a defect in the tire is discovered after the retreading operation has been accomplished, the tire must be discarded and in no event should be mounted on a vehicle because of the potential danger involved. In such an instance, the cost of the retreading materials and the labor involved in the retreading operation must be absorbed by the retreader.
In the past, defects in tires, such as nail holes, punctures and like casing defects were generally found either by visual inspection of the tire or through the use of highly sophisticated and often expensive detection equipment. By way of example, U.S. Pat. No. 5,095,744 issued to Macecek, et al. discloses tire inspection equipment having a movable energy transmitter assembly and a movable energy receiver assembly to detect energy from the transmitter assembly passing through a tire casing. In the Macecek, et al equipment, sonic or ultrasonic energy is sometimes used to find hidden defects or irregularities in a used tire casing. At other times and for or other applications electromagnetic energy or a combination of electromagnetic and sonic or ultrasonic energy is used.
U.S. Pat. No. 4,969,350 issued to Fogal, Sr. discloses a method of locating defects in tires prior to recapping in which the tire to be retreaded or recapped is placed upon an expandable mandrel and a liquid material which accentuates defects when influenced by predetermined electromagnetic wavelengths is introduced into the interior of the tire. The expandable mandrel or hub of the Fogal, Sr. equipment is expanded and the interior of the tire is pressurized after which the hub and tire are rotated. During this rotation the material is uniformly applied over the entire interior surface of the tire and due to the internal pressure, the liquid is forced to migrate through any defect toward and to the tire exterior. As the tire continues to rotate, light of the predetermined electromagnetic wavelengths corresponding to those which influence the coating material is applied to the exterior surface of the coated tire whereby any coating material which has migrated through a defect in the tire to the exterior is accentuated and thus detected.
Other prior art examples of tire inspection equipment and processes are discussed in U.S. Pat. No. 4,936,138 issued to Cushman, et al. and in U.S. Pat. No. 4,520,307 issued to Weiss, et al. The Weiss et al patent discloses a high-voltage, non-destructive inspection system for detecting nails, and/or cuts and holes in vehicle tires. The system employs a high-voltage head mounted within the tire and a reference head outside the tire opposite to the high-voltage head. The high-voltage head and reference head span the tire tread axially. The inspection is performed in one revolution of the tire. High-voltage pulses are impressed upon the high-voltage head, and the amplitude and pulse widths are variably selected, commensurate with the type of tire being tested. When a cut, hole or a nail in the tire passes between the high-voltage head and the reference head, an electric arc forms and current passes through the tire. This arc can be visually observed and also electronically detected. Upon detection, via an electronic detection circuit, a lamp lights and the tire rotation is stopped, thus facilitating location of the flaw, via a manual mode.
U.S. Pat. No. 4,936,138 issued to Cushman et al. discloses an apparatus for inspecting a tire for structural defects as the tire is rotated on a stand which comprises a movable transducer transmitter for directing a plurality of successive collimated bursts of ultrasonic energy against the tire surface, the bursts passing through the tire and forming inspection areas having the same diameter and overlapping each other as the tire is rotated during an inspection cycle. A movable receiver transducer located on the other side of the tire from the transmitter is constantly positioned to receive the collimated ultrasonic energy that passes through each inspection area. Coordination control elements are provided for moving the transmitter transducer and the receiver transducer from one side of the tire to the other generally parallel to its axis of rotation while successive ultrasonic bursts are directed through the tire as it rotates during each inspection test and while maintaining substantially the same distance between the transducers for each burst. The strength of the energy received by the receiver transducer is evaluated for each burst when the evaluation indicates that a defect is present and a visual indicator is triggered to identify the location of the structural defect in the tire being inspected.
As can be appreciated from the discussion in the preceding paragraphs, many of the prior art tire inspection methods and apparatus are quite complicated, very expensive and often not well-suited for use in the inspection of large, heavy and difficult to handle truck tires. Accordingly, it is an object of the present invention to provide an improved tire inspection apparatus that is of simple construction, is easy to use and is well-suited for the inspection of relatively heavy truck tires.